Spray gun using high pressure coating material



Nov. 23, 1965 D. J. PEEPS 3,219,279

SPRAY GUN USING HIGH PRESSURE COATING MATERIAL Filed Oct. 8, 1962 INVENTOR. DONA D paaps Q QM ATTORNEYS United States Patent 3,219,279 SPRAY GUN USING HIGH PRESSURE COATING MATERIAL Donald J. Peeps, Rossford, Ohio, assignor to The De Vilbiss Company, Toledo, Ohio, a corporation of Ohio Filed Oct. 8, 1962, Ser. No. 228,226 3 Claims. (Cl. 239-583) This invention relates to an improved spray gun in which atomization of the coating material is obtained without air and solely by the use of high pressure on the coating material. The invention is particularly di rected to a spray gun having a quick opening valve and manually-operable means to prevent opening of the valve when desired.

Spray guns utilizing high pressure coating material to obtain paint atomization without air are known in the art. The elimination of atomizing air has several advantages, the principal one of which is a reduction in the amount of overspray. In addition, some of the equipment needed to produce the pressurized air is eliminated as is the additional line for supplying air to the spray gun.

One difficulty of considerable consequence found in airless spray guns heretofore known is a brief period of improper atomization occurring when the gun is turned on or off, particularly the former, when the gun trigger is first pulled. This is caused by an excessively slow action of the coating material valve which restricts the initial flow of coating material to the nozzle when operation is begun, and sometimes the last of the coating material flowing to the nozzle when operation is stopped, so that the restricted portion of the coating material lacks sufficient pressure or force to be atomized fully when passing through the nozzle. Hence, rather than the desired fine atomization, coarse droplets are produced, known as spitting, which droplets often reach the article being coated and produce an unsightly finish.

Another problem heretofore encountered with airless spray guns is that these spray guns can be hazardous if carelessly used. Thus, the spray guns frequently carry coating material under a pressure in excess of 900 pounds per square inch which, when passed through the nozzle and finally atomized, is entirely harmless. When; however, the nozzle cap is removed for cleaning, the coating material will be emitted as a small, high pressure stream, if the trigger is pulled. This stream is emitted at a sufficient velocity, due to the high pressure involved, to pierce the hand of the operator, for example.

The airless spray gun according to the present invention overcomes the major disadvantage of spitting heretofore prevalent and also overcomes the hazardous disadvantage of accidental discharge. The spray gun according to the invention has a quick opening valve, actuated in response to pressure differentials and which immediately moves to a fully opened position when initially moved by the trigger so that the stream immediately emerges, fully atomized, from the nozzle. The valve can also be closed quickly enough by the operator to prevent spitting during this movement. The spray gun according to the invention also includes a device which can be operated when the gun is not being used, and particularly when the nozzle cap is removed, to prevent accidental discharge of a dangerous, high velocity stream of the coating material.

It is, therefore, a principal object of the invention to provide a spray gun having the advantages set forth above.

Other objects and advantages of the invention will be apparent from the following detailed description of a 3,219,279 Patented Nov. 23, 1965 preferred embodiment thereof, reference being made to the accompanying drawing, in which:

FIG. 1 is a side view in elevation with parts broken away and with parts in cross section, of an airless spray gun embodying the present invention;

FIG. 2 is an enlarged, fragmentary view in cross section of a portion of the spray gun shown in FIG. 1; and

FIG. 3 is a front view, with parts broken away and with parts in cross section, of the spray gun shown in FIG. 1.

Referring to the drawing, and more particularly to FIG. 1, a spray gun embodying the principles of the invention is indicated at 10 and is supplied with coating material through a line 12 from a pump 14 which receives it from a suitable source 16. The spray gun 10 is somewhat similar to conventional hand operated spray guns heretofore known, with one principal difference being that the present spray gun does not have any air passages therein. The coating material under high pressure passes through a supply nipple 18 to a rear chamber 20 from which it flows past a valve assembly indicated generally at 22, when opened, and through an opening 24 in a nozzle cap 26 from which it is emitted as a finely divided atomized spray. It will be readily appreciated that if the valve assembly 22 is not opened and closed extremely rapidly, the initial and the last of the coating material will be somewhat restricted by the valve assembly so that the material will not reach the cap 26 at the proper pressure and velocity. Consequently, this initial and last coating material will sputter or spit from the cap 26 in the form of coarse, unatomized droplets.

The spray gun according to the present invention is provided with a stepped bore 25 leading to the discharge orifice 24 that is purposely maintained as small as possible and yet of sufficient size to feed the small passage that terminates in the orifice. For example, if the passage terminating in orifice 24 is .025" in diameter the passage 25 leading to it would be only about .031. In many solid spray guns a substantial quantity of liquid is present between the valve seat and the discharge orifice, which liquid seriously slows the discharge when spraying first begins and constitutes a well of dormant material. By extracting energy from the discharge liquid, the dormant body robs it of the power to be atomized properly and spitting occurs. By contrast, the present invention teaches the maintenance of a mass of liquid as small as possible between the valve seat and the discharge orifice. This leads to good and immediate atomization.

The valve assembly 22 of the present invention is capable of extremely rapid opening and closing to eliminate spitting. The assembly 22, according to the invention, includes a valve body 28 having a large or blunt end 30 which preferably is hemispherical, as shown, but which can also assume other configurations, so long as the effective area exposed to paint pressure when the valve is cracked open or first moved from its seat is large, as hereinafter described. Guide vanes 34 are afiixed to the rear end of the valve body 28 and are in slidable contact with a guide passage 36 to aid in maintaining the valve body 28 centered, which helps the valve assembly 22 to close rapidly. The valve assembly 22 cooperates with a valve seat member 38 centrally located in the passage 32 and adapted to engage the front end of the valve body 28. A hemispherical valve seat 40 is provided for valving relationship with the blunt end 30 of the valve body.

The valve assembly 22 is operated through a valve rod 44 which extends rearwardly through a packing 46, held by a retainer 48, to a pivotable trigger 50. The rod 44 actually extends through a slot 52 in the trigger 50 and, in the form shown, through a Contact shoe 54 bent around 3 a portion of the trigger 5t), and finally terminates in an enlarged shoulder flange 56 and a plastic bumper 58. The latter two are located in a recess 60 of a collar 62 which is held in a spring passage 64 by the shoe 54 and acts as a retainer for a spring 66 therein. The spring 66 is located around a positioning rod 68 and is held in adjustable compression by a threaded spring retainer 70. When the trigger 50 is initially pulled, the shoe 54 first pushes the collar 62 rearwardly against spring 66 to separate the bumper 58 and the end of the recess 60. This positions the rod 44 and the valve body 28 for free and unobstructed rearward movement, although the body 28 is still held against the Valve seat 40 by the pressure of the coating material in the chamber 20, as hereinafter described. When the trigger 50 is moved further toward the rear, the shoe 54 then engages the flange 56 and pulls the rod 44 rearwardly. The instant this happens, and the large end 30 of the valve moves away from the valve seat 40 of the seating member 38, the high pressure coating material moves therebetween and instantaneously exerts a rearward force on the valve body 28 through the end 30. The effective area of the left end of the body 28 upon which the coating material pressure acts exceeds the effective area of the right end on which the coating material acts because the latter end includes the cross-sectional area of the valve rod 44 which is acted upon only by atmospheric pressure outside the retainer 48. Consequently, the body 28 is moved rearwardly almost instantaneously, due to the force of the coating material acting rearwardly on the larger effective area of the valve body 28, along with the rearward force exerted on the trigger 50 by the valve operator.

It will be seen that the annular area of the valve body around the rod 44 serves to maintain the valve body in seated position once the valve is closed. The spring 66, therefore, must be heavy enough to close the valve, but the force required for firm seating to prevent dripping can be derived from the hydraulic force acting on the rear of the valve body.

Initially, the force of the coating material between the seating member 38 and the large end 30 of the valve causes the valve body 28 to move rearwardly faster than the trigger 50 can be pulled which results in the rapid valve action and eliminates spitting. The excess speed of the valve body 28 occurs until the bumper 58 hits the end of the recess 60 again and the trigger 50 catches up with the shoulder flange 56 again. No corresponding fast action of the valve assembly 22 occurs when spraying is stopped, but it has been found that the valve assembly 22 closes sufliciently quickly to prevent spitting when the operator simply releases the trigger 50. Thus, the valve assembly and operating mechanism according to the invention enables a clean, finely atomized spray to be initiated and stopped Without spitting and without its concommitant disadvantages hereofore commonly encountered.

It will be appreciated that if the nozzle cap 26 is removed, and the trigger 50 is pulled, the coating material will again flow past the valve body 28 and through the passage 25, but, with the restrictive nozzle opening 24 no longer present, will issue as a single, dense and solid stream from the passage 25 and to the nozzle opening. This stream may have sufficient power to penetrate the skin of an operator standing in front of it or at the least to quickly deposit coating material over a very wide area. To prevent such unfortunate results from occurring, the gun is provided with a safety device to prevent the trigger 50 from being pulled, whenever desired. Accordingly, thetrigger 50 has legs 72 which extend upwardly on each side of the gun body and receive a pin 74 which pivotally supports the trigger 50. In this instance, a lock pin 76 extends through the legs 72 below the pivot point and through a hole '78 in the gun body, which hole is much larger than the pin 76 so that the pin can move laterally therein and thereby enable the trigger 50 to pivot about the pin 74. However, when the pin 76 is held against the forward side of the opening 78 by a restaining rod 80, it holds the trigger in an immovable position with the valve assembly 22 closed. The gun then cannot be accidentally operated. The position of the restraining pin 80 is manually controlled by a knob member 82 which is threadedly engaged in a retainer 84 and has threads of long pitch so that only 4 or /2 turn of the knob member 82 will move the pin 80 into or out of the blocking position in the passage 78.

Various modifications of the above described embodiment of the invention will be apparent to those skilled in the art and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and tenor of the accompanying claims.

What I claim is:

1. A spray gun comprising a valve for controlling flow of coating material, a trigger for operating said valve, means for pivotally supporting said trigger from a body of the spray gun, said trigger having a first position in which said valve is closed, and a second position pivotally spaced from the first in which said valve is open, safety means having a first position in the pivotal path of the trigger for preventing pivotal movement of same, and a second position spaced from the pivotal path so that said trigger can pivot between the first and the second position, said safety means being threadedly engaged with said gun body by threads of long pitch, and a rotatable knob attached to said safety means for moving said last-named safety means between its first position and second position by a fraction of one revolution of said knob.

2. A spray gun comprising a gun body forming a coating material passage, nozzle means located beyond one end of said passage, means forming a valve seat adjacent said one end of said passage, said valve seat facing toward coating material passage, a valve body in said coating material passage, said valve bodyhaving a blunt end fitting closely with said valve seat when said valve body is in a closed position, and spaced from said seat when said valve body is in an open position, a valve rod' extending from said valve body out of said coating material passage in a direction away from said valve seat, with the effective area against which hydraulic pressure in said passage can act on said body to urge said body toward said seat being reduced by the cross-sectional area of said rod, said valve rod having a flange outside said gun body, a collar engageable with said valve rod, resilient means supported by said gun body and contacting and urging said collar toward said valve rod, said collar normally urging said valve body against said valve seat, a

trigger supported by said gun body, said trigger having means positioned adjacent said valve rod between said coating material passage and said flange eflective, prior to engagement with said flange, to engage and move said collar rearwardly away from said valve rod a predetermined amount, and then engage and move rearwardly said valve rod flange, said valve rod and said flange being capable of rearward movement relative to said'trigger, whereby said collar is spaced from said valve rod by the predetermined amount before said valve rod flange is engaged and moved rearwardly by said trigger means, said valve body being opened and said valve rod being moved further rearwardly by coating material pressure acting on the valve seat end of said body until said rod again contacts said collar.

3. A spray gun comprising a gun body forming a coating material passage, nozzle means located beyond one end of said passage, means forming a valve seat adjacent said one end of said passage, said valve seat facing toward coating material passage, a valve body in said coating material passage, said valve body having a valve seat end fitting closely with said valve seat when said valve body is in a closed position, and spaced from said seat when said valve body is in an open position, a valve rod extending from said valve body out of said coating material passage in a direction away from said valve seat, with the eifective area against which hydraulic pressure in said passage can act on said body to urge said body toward said seat being reduced by the cross-sectional area of said rod, said valve rod having a flange outside said gun body, a collar engageable with said valve rod, resilient means supported by said gun body and contacting and urging said collar toward said valve rod, said collar normally being in contact with said valve rod and urging said valve body against said valve seat, said gun body having means for restricting movement of said collar generally to a direction parallel to the longitudinal extent of said valve rod, a trigger pivotally supported by said gun body and having an opening in which a portion of said valve rod between the coating material passage and said flange is received, said trigger adjacent said opening contacting said collar when said trigger is moved rearwardly to move said collar and said resilient means rearwardly without moving said valve rod and said flange to space apart said collar and said valve rod a predetermined distance, said trigger subsequently engaging said valve rod flange and moving it rearwardly upon continued movement of said trigger whereby fluid pressure in said passage can act upon the valve seat end of said valve body and force said body and said valve rod rearwardly against said collar without further movement of said trigger.

References Cited by the Examiner UNITED STATES PATENTS 1,910,909 5/1933 Werder 2511l2 X 2,991,940 7/1961 Dupler et a1. 239583 X 3,000,576 9/1961 Levey et al. 239-583 X RAPHAEL M. LUPO, Primary Examiner.

LOUIS I. DEMBO, Examiner. 

1. A SPRAY GUN COMPRISING A VALVE FOR CONTROLLING FLOW OF COATING MATERIAL, A TRIGGER FOR OPERATING SAID VALVE, MEANS FOR PIVOTALLY SUPPORTING SAID TRIGGER FROM A BODY OF THE SPRAY GUN, SAID TRIGGER HAVING A FIRST PORTION IN WHICH SAID VALVE IS CLOSED, AND A SECOND POSITION PIVOTALLY SPACED FROM THE FIRST IN WHICH SAID VALVE IS OPEN, SAFETY MEANS HAVING A FIRST POSITION IN THE PIVOTAL PATH OF THE TRIGGER FOR PREVENTING PIVOTAL MOVEMENT OF SAME, AND A SECOND POSITION SPACED FROM THE PIVOTAL PATH SO THAT SAID TRIGGER CAN PIVOT BETWEEN THE FIRST AND THE SECOND POSITION, SAID SAFETY MEANS BEING THREADEDLY ENGAGED WITH SAID GUN BODY BY THREADS OF LONG PITCH, AND A ROTATABLE KNOB ATTACHED TO SAID SAFETY MEANS FOR MOVING SAID LAST-NAMED SAFETY MEANS BETWEEN ITS FIRST POSITION AND SECOND POSITION BY A FRACTION OF ONE REVOLUTION OF SAID KNOB. 